Blood pressure information measurement devices obtain blood pressure information of a measurement subject. The blood pressure information obtained by such blood pressure information measurement devices includes various types of information related to the circulatory system of the measurement subject, such as a systolic blood pressure value (a maximum blood pressure value), a diastolic blood pressure value (a minimum blood pressure value), an average blood pressure value, a sphygmogram, pulse, AI (Augmentation Index) value, and the like of the measurement subject, and so on. Stress on the heart of the measurement subject, changes in the hardness of arteries of the measurement subject, or the like can be understood based on this blood pressure information. A blood pressure information measurement device is used in the early detection, prevention, treatment, and so on of a measurement subject's circulatory system conditions.
Generally speaking, a blood pressure information measurement device cuff (called simply a “cuff” hereinafter) is used in the measurement of blood pressure information. The cuff is a band-shaped member having an inner cavity, and is wrapped around a part of a body such as an upper arm. The cuff contains a fluid bladder for pressurizing the body (an artery).
In a blood pressure information measurement device used to measure blood pressure values such as a systolic blood pressure value or a diastolic blood pressure value (called simply a “sphygmomanometer” hereinafter), the cuff is wrapped around the surface of part of the body, and a fluid such as air, a liquid, or the like is injected into and exhausted from the fluid bladder contained in the cuff. The fluid bladder inflates and deflates when the fluid is injected or exhausted, and a change in the inner pressure of the fluid bladder produced at this time is obtained as an arterial pulse wave or a blood pressure value.
FIG. 14 is a plan view illustrating a typical cuff 100A in an unrolled state. In FIG. 14, part of an outer cover 30 is illustrated in a broken manner, but in reality, the outer cover 30 continues through that part. The same applies to FIG. 15, described later.
Referring to FIG. 14, the cuff 100A includes the outer cover 30, an air bladder (not shown) contained as a fluid bladder within the outer cover 30, a surface fastener 41, and a surface fastener 42.
The outer cover 30, meanwhile, has a front surface 31, a rear surface 32, one end portion 30a, another end portion 30b, one side portion 30c, and another side portion 30d. 
The air bladder is connected to an air tube 80 while being contained within the outer cover 30. The air bladder is provided toward the one end portion 30a in the lengthwise direction of the outer cover 30. The “lengthwise direction” mentioned here refers to the direction that connects the one end portion 30a and the other end portion 30b of the outer cover 30.
The surface fastener 41 is provided upon the front surface 31 of the outer cover 30. The surface fastener 42 is provided upon the rear surface 32 of the outer cover 30. The surface fastener 41 and the surface fastener 42 are capable of interlocking with each other.
The cuff 100A is worn so that the rear surface 32 of the outer cover 30 and the body (not shown) are opposed to each other (see FIG. 16). The cuff 100A is wrapped around the body in a ring shape. Fastening the surface fastener 41 and the surface fastener 42 to each other holds the outer cover 30, which has been wrapped into a ring shape, on the body in a secured state. The air bladder contained within the outer cover 30 is thus anchored to the body, and the blood pressure information can then be measured. A cuff having essentially the same configuration as the cuff 100A is disclosed in JP 2004-166943A (Patent Literature 1), below.
Another form of the outer cover 30 will be described with reference to FIG. 15. As exemplified by the outer cover 30 of a cuff 100B, some configurations have the outer cover 30 gradually becoming narrower as the outer cover 30 progresses from the one end portion 30a to the other end portion 30b. Although the outer cover 30 of the cuff 100B is configured so that the outer cover 30 narrows only on the side portion 30d, there are also configurations in which the outer cover 30 narrows on both the side portion 30c and the side portion 30d. 
Referring to FIG. 16, there are cases where, when the cuff 100A is, for example, wrapped around an upper arm 70, the cuff 100A is fastened with the other end portion 30b of the outer cover 30 shifted toward the shoulder. The side portion 30c of the outer cover 30 in the vicinity of the other end portion 30b is disposed protruding from the front surface 31 of the outer cover 30 (on the side of the one end portion 30a) that has already been wrapped, toward the outer side (that is, the surface of the upper arm 70). The greater the difference between a length H1 around the upper arm 70 near the shoulder and a length H2 around the upper arm 70 near the elbow is, the greater the shift toward the shoulder will be when the other end portion 30b of the outer cover 30 is fastened.
In this case, the contact surface area is low between the surface fastener 41 and the surface fastener 42, and thus the surface fastener 41 and the surface fastener 42 have a low fastening force. The air bladder therefore cannot be inflated or deflated to the desired pressure, and this can also cause the cuff 100A to separate from the upper arm 70 while measuring the blood pressure value. As a result, variations occur in the measured values, which makes it difficult to measure the blood pressure information in an accurate and stable manner. Likewise, when the cuff 100B shown in FIG. 15 is, for example, wrapped around the upper arm 70, the contact surface area between the surface fastener 41 and the surface fastener 42 drops, variations in the measured values occurs, and it becomes difficult to measure the blood pressure information in an accurate and stable manner.
Referring to FIG. 17, there are also cases where when the cuff 100A is wrapped around the upper arm 70, the cuff 100A is wrapped so that the surface fastener 42 visibly overlaps with the surface fastener 41. To rephrase, the side portion 30c of the outer cover 30 near the other end portion 30b is disposed so as to overlap with the side portion 30c of the outer cover 30 that is already wrapped around the upper arm 70 (that is, on the side of the one end portion 30a). Likewise, the side portion 30d of the outer cover 30 near the other end portion 30b is disposed so as to overlap with the side portion 30d of the outer cover 30 that is already wrapped around the upper arm 70 (that is, on the side of the one end portion 30a).
In this case, a greater difference between the aforementioned length H1 in the aforementioned length H2 results in an insufficient length on the side of the side portion 30d of the outer cover 30 (that is, the side closer to the elbow) and an excessive length on the side of the side portion 30c of the outer cover 30 (that is, the side closer to the shoulder), and thus a gap S is formed between the surface fastener 41 and the surface fastener 42.
Due to the gap S, the contact surface area between the surface fastener 41 and the surface fastener 42 decreases, and thus the fastening force between the surface fastener 41 and the surface fastener 42 is reduced. The air bladder therefore cannot be inflated and deflated to the desired pressure, and this can also cause the cuff 100A to separate from the upper arm 70 while measuring the blood pressure value. As a result, variations occur in the measured values, which makes it difficult to measure the blood pressure information in an accurate and stable manner.
Patent Literature 1: JP 2004-166943A